Semiconductor light-emitting devices, such as light emitting diodes (LED), are formed by using semiconductor materials. The semiconductor light emitting devices are one kind of minute solid-state light sources that can transform electrical energy into light energy. The semiconductor light emitting devices are not only small in volume, rapid in response speed, shockproof, long-lived, and use a low driving voltage, but also can meet the lightness, thinness, and miniaturization needs of various apparatuses, and thus have become very popular electric products in daily life.
In recent years, a great deal of attention has been directed to the light-emitting devices utilizing nitride-based semiconductors such as GaN, AlGaN, InGaN and AlInGaN. Usually, most of the light-emitting devices of the aforementioned type are grown on an electrically insulating sapphire substrate, which is different from other light-emitting devices utilizing conductive substrates.
Currently, when manufacturing a light-emitting device composed of nitride-based semiconductors, an AlInGaN material is grown at low temperature directly on a sapphire substrate to be used as a buffer layer. The dislocation density of the buffer layer is greatly increased, and the life of the light-emitting device is thereby reduced and the performance of the light-emitting device is degraded.